JP2000183681A - Surface acoustic wave device - Google Patents
Surface acoustic wave deviceInfo
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- JP2000183681A JP2000183681A JP10354631A JP35463198A JP2000183681A JP 2000183681 A JP2000183681 A JP 2000183681A JP 10354631 A JP10354631 A JP 10354631A JP 35463198 A JP35463198 A JP 35463198A JP 2000183681 A JP2000183681 A JP 2000183681A
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- Prior art keywords
- acoustic wave
- surface acoustic
- electrode
- saw
- width
- Prior art date
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- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、電気信号と弾性表
面波との間の変換を行うすだれ状電極を有する弾性表面
波装置に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device having an interdigital transducer for converting between an electric signal and a surface acoustic wave.
【０００２】[0002]
【従来の技術】近年、携帯電話やテレビ受像機等の電子
部品や通信部品において、共振子や帯域フィルタとして
弾性表面波装置（ＳＡＷ（Ｓｕｒｆａｃｅ Ａｃｏｕｓ
ｔｉｃＷａｖｅ）デバイス）が使用されている。2. Description of the Related Art In recent years, in electronic parts and communication parts such as mobile phones and television receivers, surface acoustic wave devices (SAW (Surface Acoustics) have been used as resonators and bandpass filters.
ticWave) device).
【０００３】図７は、従来のＳＡＷデバイスの一例を示
す平面図である。FIG. 7 is a plan view showing an example of a conventional SAW device.
【０００４】このＳＡＷデバイス１は、１ポート型ＳＡ
Ｗ共振子であり、圧電基板２とすだれ状電極である櫛形
電極（ＩＤＴ（Ｉｎｔｅｒ Ｄｉｇｉｔａｌ Ｔｒａｎ
ｓｄｕｃｅｒ））３及び反射器４等で大略構成されてい
る。[0004] This SAW device 1 is a one-port SA.
A W-resonator, a piezoelectric substrate 2 and a comb-shaped electrode (IDT (Inter Digital Tran
sducer)) 3 and a reflector 4.
【０００５】圧電基板２は、例えば水晶で矩形板状に形
成されている。ＩＤＴ３及び反射器４は、圧電基板２の
表面に導体金属を蒸着あるいはスパッタリング等により
薄膜状に形成した上で、フォトリソグラフィ等によりす
だれ状となるように形成されている。具体的には、ＩＤ
Ｔ３は、複数の電極指３ａが所定のピッチで並設されて
長手方向の各端部が交互に短絡されるように形成されて
いる。即ち、２つの櫛形状の電極の各櫛歯部分が、所定
距離隔てて互い違いに入り込むように形成されている。
このＩＤＴ３は、電気的に接続されている外部端子５を
介して電気信号とＳＡＷとの間の変換を行う機能を有す
る。反射器４は、複数の電極指４ａが所定のピッチで並
設されて長手方向の各両端部が短絡されるように形成さ
れている。そして、同一構成の２つの反射器４が、電極
指４ａがＩＤＴ３の電極指３ａと平行になるように、か
つＩＤＴ３をＳＡＷの伝播方向、即ちＩＤＴ３の電極指
３ａの長手方向に直交する方向に所定距離隔てて挟み込
むように形成されている。この反射器４は、ＩＤＴ３か
ら伝搬してくるＳＡＷを反射して、ＳＡＷのエネルギを
内部に閉じこめる機能を有する。The piezoelectric substrate 2 is formed in a rectangular plate shape, for example, from quartz. The IDT 3 and the reflector 4 are formed in such a manner that a conductive metal is formed on the surface of the piezoelectric substrate 2 into a thin film by vapor deposition, sputtering, or the like, and then interdigitated by photolithography or the like. Specifically, ID
T3 is formed such that a plurality of electrode fingers 3a are arranged side by side at a predetermined pitch, and each end in the longitudinal direction is alternately short-circuited. That is, the respective comb teeth portions of the two comb-shaped electrodes are formed so as to alternately enter at a predetermined distance.
The IDT 3 has a function of performing conversion between an electric signal and SAW via an external terminal 5 that is electrically connected. The reflector 4 is formed such that a plurality of electrode fingers 4a are juxtaposed at a predetermined pitch and both ends in the longitudinal direction are short-circuited. Then, the two reflectors 4 having the same configuration are arranged so that the electrode finger 4a is parallel to the electrode finger 3a of the IDT 3 and the IDT 3 is moved in the SAW propagation direction, that is, in the direction orthogonal to the longitudinal direction of the electrode finger 3a of the IDT 3. It is formed so as to be sandwiched at a predetermined distance. The reflector 4 has a function of reflecting the SAW propagating from the IDT 3 and confining the energy of the SAW inside.
【０００６】このような構成において、電気信号が、外
部端子５を介してＩＤＴ３に入力されると、圧電効果に
よりＳＡＷに変換される。このＳＡＷは、ＩＤＴ３の電
極指３ａの長手方向に対して直交方向に伝搬され、ＩＤ
Ｔ３の両側から反射器４に放射される。このとき、圧電
基板２の材質、電極の厚みや電極の幅等で決定される伝
播速度とＩＤＴ３の電極指３ａの電極周期ｄ0 に等しい
波長を持つＳＡＷが、最も強く励振される。このＳＡＷ
は、反射器４により多段反射されてＩＤＴ３に戻され、
図８に示す共振周波数付近の周波数（動作周波数）ｆv
のみの電気信号に変換されてＩＤＴ３から外部端子５を
介して出力される。In such a configuration, when an electric signal is input to the IDT 3 via the external terminal 5, it is converted into a SAW by a piezoelectric effect. This SAW is propagated in a direction perpendicular to the longitudinal direction of the electrode finger 3a of the IDT 3, and the ID
The light is radiated to the reflector 4 from both sides of T3. In this case, the material of the piezoelectric substrate 2, the SAW having a wavelength equal to the electrode period d 0 of the electrode fingers 3a of the propagation velocity and IDT3 determined by width of the thickness of the electrode and the electrode is most strongly excited. This SAW
Is reflected by the reflector 4 in multiple stages and returned to the IDT 3,
A frequency (operating frequency) f v near the resonance frequency shown in FIG.
The signal is converted into an electric signal of only the IDT 3 and output from the IDT 3 via the external terminal 5.
【０００７】図９は、従来のＳＡＷデバイスの別の一例
を示す平面図である。FIG. 9 is a plan view showing another example of a conventional SAW device.
【０００８】このＳＡＷデバイス１１は、トランスバー
サル型ＳＡＷフィルタであり、圧電基板１２とすだれ状
電極であるＩＤＴ１３等で大略構成されている。圧電基
板１２は、例えば水晶で矩形板状に形成されている。Ｉ
ＤＴ１３は、圧電基板１２の表面に導体金属を蒸着ある
いはスパッタリング等により薄膜状に形成した上で、フ
ォトリソグラフィ等によりすだれ状となるように形成さ
れている。具体的には、ＩＤＴ１３は、複数の電極指１
３ａが所定のピッチで並設されて長手方向の各端部が交
互に短絡されるように形成されている。即ち、２つの櫛
形状の電極の各櫛歯部分が、所定距離隔てて互い違いに
入り込むように形成されている。さらに、各電極指１３
ａは、全体として２分の１周期の正反転の余弦カーブ
（図示一点鎖線）を描くように長手方向の途中部分が分
断されている。このように、電極指１３ａに対して重み
付けを実施することにより、図８に示す周波数ｆs 付近
の横モードスプリアスの発生を低減することができる。The SAW device 11 is a transversal type SAW filter, and generally comprises a piezoelectric substrate 12 and IDTs 13 which are interdigital electrodes. The piezoelectric substrate 12 is formed of, for example, quartz in a rectangular plate shape. I
The DT 13 is formed by forming a conductive metal on the surface of the piezoelectric substrate 12 into a thin film by vapor deposition or sputtering or the like, and then forming the thin film by photolithography or the like. Specifically, the IDT 13 includes a plurality of electrode fingers 1.
3a are arranged side by side at a predetermined pitch so that each end in the longitudinal direction is alternately short-circuited. That is, the respective comb teeth of the two comb-shaped electrodes are formed so as to alternately enter at a predetermined distance. Furthermore, each electrode finger 13
As for a, the middle part in the longitudinal direction is divided so as to draw a cosine curve (a dashed line in the drawing) of a half inversion and a positive inversion as a whole. Thus, by performing the weighted electrode finger 13a, it is possible to reduce the occurrence of transverse mode spurious response around a frequency f s shown in FIG.
【０００９】図１０は、従来のＳＡＷデバイスのさらに
別の一例を示す平面図である。FIG. 10 is a plan view showing still another example of the conventional SAW device.
【００１０】このＳＡＷデバイス２１は、横結合型ＳＡ
Ｗフィルタであり、圧電基板２２とすだれ状電極である
ＩＤＴ２３及び反射器２４等で大略構成されている。圧
電基板２２は、例えば水晶で矩形板状に形成されてい
る。ＩＤＴ２３及び反射器２４は、圧電基板２２の表面
に導体金属を蒸着あるいはスパッタリング等により薄膜
状に形成した上で、フォトリソグラフィ等によりすだれ
状となるように形成されている。具体的には、ＩＤＴ２
３及び反射器２４は、図７に示すＩＤＴ３及び反射器４
を電極指３ａ、４ａの長手方向に２組並べて結合配置し
た形状に形成されている。このようなＩＤＴ２３及び反
射器２４とすることにより、広帯域化及び遅延特性を向
上させることができる。The SAW device 21 has a laterally coupled SA.
The filter is a W filter, and generally includes a piezoelectric substrate 22 and IDTs 23, which are interdigital electrodes, a reflector 24, and the like. The piezoelectric substrate 22 is formed, for example, of quartz into a rectangular plate shape. The IDT 23 and the reflector 24 are formed in such a manner that a conductive metal is formed on the surface of the piezoelectric substrate 22 in a thin film shape by vapor deposition or sputtering, and then formed into an interdigital shape by photolithography or the like. Specifically, IDT2
The IDT 3 and the reflector 4 shown in FIG.
Are arranged in a longitudinal direction of the electrode fingers 3a and 4a and are combined and arranged. With such an IDT 23 and reflector 24, it is possible to increase the bandwidth and improve the delay characteristics.
【００１１】[0011]
【発明が解決しようとする課題】上述した図７の従来の
１ポート型ＳＡＷ共振子は、ＳＡＷの伝播方向の電極指
３ａの幅ｗ0 が、長手方向にわたって均一に形成されて
いるため、その長手方向のＳＡＷの伝播速度の分布は一
定となる。従って、ＳＡＷの変位分布は、複数の電極指
３ａの重なり部分（以下、交差指という）の全体に分散
し、交差指の長さｌ0 を長くすると、横モードスプリア
スが主振近辺に表れる現象、即ち図８に示す横モードス
プリアスの周波数ｆs と主振の動作周波数ｆv との差Δ
ｆが小さくなり、周波数の安定した発振器を得ることが
難しい。In the above-described conventional one-port SAW resonator shown in FIG. 7, the width w 0 of the electrode finger 3a in the SAW propagation direction is uniform over the longitudinal direction. The distribution of the SAW propagation speed in the longitudinal direction is constant. Therefore, the displacement distribution of the SAW is dispersed throughout the overlapping portion (hereinafter, referred to as the cross finger) of the plurality of electrode fingers 3a, and when the length l 0 of the cross finger is increased, the transverse mode spurious appears near the main vibration. That is, the difference Δ between the frequency f s of the transverse mode spurious and the operating frequency f v of the main vibration shown in FIG.
Since f becomes small, it is difficult to obtain an oscillator having a stable frequency.
【００１２】図９の従来のトランスバーサル型ＳＡＷフ
ィルタは、電極指１３ａの交差指の長さが、ＳＡＷの伝
播方向に余弦カーブを描くように変化して形成されてい
るので、横モードスプリアスの発生を抑圧することがで
きる。ところが、電極指１３ａの分断されて孤立した部
分１３ａａは、ＩＤＴ１３として機能しないにもかかわ
らず、孤立部分１３ａａの面積は、ＩＤＴ１３の面積の
３０％に達するため、フィルタ自体が大型化する。In the conventional transversal type SAW filter shown in FIG. 9, since the length of the cross finger of the electrode finger 13a is changed so as to draw a cosine curve in the SAW propagation direction, the transverse mode spurious is reduced. Occurrence can be suppressed. However, the area of the isolated portion 13aa reaches 30% of the area of the IDT 13 although the separated and isolated portion 13aa of the electrode finger 13a does not function as the IDT 13, so that the filter itself becomes large.
【００１３】図１０の従来の横結合型ＳＡＷフィルタ
は、通過帯域幅が、主振の動作周波数と斜対称モードの
周波数の差によって決定される。従って、通過帯域幅を
広げるためには、電極指２３ａ交差指の長さｌ2 を短く
しなければならないが、交差指の長さｌ2 を短くする
と、ＩＤＴ２３の面積が減少して、特性インピーダンス
が増加する。In the conventional laterally coupled SAW filter shown in FIG. 10, the pass bandwidth is determined by the difference between the main operating frequency and the frequency of the oblique symmetric mode. Therefore, in order to widen the pass band width, the length l 2 of the interdigital finger 23a must be shortened. However, if the length l 2 of the interdigital finger is shortened, the area of the IDT 23 is reduced and the characteristic impedance is reduced. Increase.
【００１４】本発明の目的は、上記課題を解消して、横
モードスプリアスが低減され特性インピーダンスが改善
されたＳＡＷ装置を提供することである。An object of the present invention is to solve the above-mentioned problems and to provide a SAW device in which transverse mode spurious is reduced and characteristic impedance is improved.
【００１５】[0015]
【課題を解決するための手段】請求項１の発明は、電気
信号と弾性表面波との間の変換を行うすだれ状電極が形
成されている圧電基板を備えた弾性表面波装置におい
て、前記すだれ状電極が、前記弾性表面波の伝播方向の
電極指の幅に変化を付けて形成されていることを特徴と
する弾性表面波装置である。According to a first aspect of the present invention, there is provided a surface acoustic wave device provided with a piezoelectric substrate having an interdigital transducer for converting between an electric signal and a surface acoustic wave. The shape electrode is formed by changing the width of the electrode finger in the propagation direction of the surface acoustic wave.
【００１６】この請求項１の発明では、電極指の幅が弾
性表面波の伝播直交方向に変化しているので、弾性表面
波の伝播速度を変化させてエネルギを閉じ込め、弾性表
面波の変位を電極指の変化部分に集中させることができ
る。In the first aspect of the present invention, since the width of the electrode finger changes in the direction orthogonal to the propagation of the surface acoustic wave, energy is confined by changing the propagation speed of the surface acoustic wave, and the displacement of the surface acoustic wave is reduced. It is possible to concentrate on the changing part of the electrode finger.
【００１７】請求項２の発明は、請求項１記載の構成に
おいて、前記すだれ状電極が、櫛形電極及び反射器で構
成されており、少なくとも前記櫛形電極が、前記弾性表
面波の伝播方向の前記電極指の幅に変化を付けて形成さ
れている弾性表面波装置である。According to a second aspect of the present invention, in the configuration according to the first aspect, the interdigital transducer comprises a comb-shaped electrode and a reflector, and at least the comb-shaped electrode is arranged in the propagation direction of the surface acoustic wave. This is a surface acoustic wave device formed by changing the width of an electrode finger.
【００１８】この請求項２の発明では、弾性表面波の伝
播速度を変化させてエネルギを閉じ込め、弾性表面波の
変位を電極指の変化部分に集中させることが、反射器に
よりさらに効率良く行うことができる。According to the second aspect of the present invention, the energy is confined by changing the propagation speed of the surface acoustic wave, and the displacement of the surface acoustic wave is concentrated on the changed portion of the electrode finger by the reflector. Can be.
【００１９】請求項３の発明は、請求項１または２記載
の構成において、前記すだれ状電極の電極指における変
化部分が、前記弾性表面波の伝播方向に延びる前記すだ
れ状電極の中心線に対して対称に形成されている弾性表
面波装置である。According to a third aspect of the present invention, in the configuration according to the first or second aspect, the changing portion of the electrode finger of the interdigital electrode is positioned with respect to a center line of the interdigital electrode extending in a propagation direction of the surface acoustic wave. This is a surface acoustic wave device formed symmetrically.
【００２０】この請求項３の発明では、電極指の変化部
分が弾性表面波の伝播直交方向に対称形状であるので、
弾性表面波の変位を電極指の変化部分に効率良く集中さ
せることができる。According to the third aspect of the present invention, since the changing portion of the electrode finger is symmetrical in the direction orthogonal to the propagation of the surface acoustic wave,
The displacement of the surface acoustic wave can be efficiently concentrated on the changed part of the electrode finger.
【００２１】請求項４の発明は、請求項１、２または３
記載の構成において、前記すだれ状電極の電極指におけ
る変化部分の幅が、他の部分の幅より狭くなるように形
成されている弾性表面波装置である。[0021] The invention of claim 4 is the invention of claim 1, 2 or 3.
The surface acoustic wave device according to the above configuration, wherein a width of a changing portion of the electrode finger of the interdigital electrode is smaller than a width of another portion.
【００２２】この請求項４の発明では、電極指の幅を狭
くしているので、各電極指の交差部分の長さを短くする
必要がなくなる。According to the fourth aspect of the present invention, since the width of the electrode finger is reduced, it is not necessary to reduce the length of the intersection of each electrode finger.
【００２３】請求項５の発明は、請求項１、２、３また
は４記載の構成において、前記すだれ状電極の電極指に
おける変化部分が、重み付けされて形成されている弾性
表面波装置である。According to a fifth aspect of the present invention, there is provided a surface acoustic wave device according to any one of the first to third aspects of the present invention, wherein the changing portion of the interdigital electrode is weighted.
【００２４】請求項６の発明は、請求項５記載の構成に
おいて、前記重み付けが、前記弾性表面波の伝播直交方
向の前記電極指の変化部分の長さである弾性表面波装置
である。A sixth aspect of the present invention is the surface acoustic wave device according to the fifth aspect, wherein the weighting is a length of a changing portion of the electrode finger in a direction orthogonal to the propagation of the surface acoustic wave.
【００２５】この請求項５または６の発明では、すだれ
状電極全面を機能させることができるので、従来のすだ
れ状電極の面積より小さくしても、従来の弾性表面波装
置と同等の特性を得ることができる。According to the fifth or sixth aspect of the present invention, since the entire surface of the interdigital transducer can be made to function, even if the area of the interdigital transducer is smaller than that of the conventional interdigital transducer, characteristics equivalent to those of the conventional surface acoustic wave device can be obtained. be able to.
【００２６】[0026]
【発明の実施の形態】以下、本発明の好適な実施の形態
を図面に基づいて説明する。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.
【００２７】図１は、本発明のＳＡＷデバイスの実施形
態を示す平面図である。FIG. 1 is a plan view showing an embodiment of a SAW device according to the present invention.
【００２８】このＳＡＷデバイス３１は、１ポート型Ｓ
ＡＷ共振子であり、圧電基板３２とすだれ状電極である
櫛形電極（ＩＤＴ（Ｉｎｔｅｒ Ｄｉｇｉｔａｌ Ｔｒ
ａｎｓｄｕｃｅｒ））３３及び反射器３４等で大略構成
されている。This SAW device 31 is a one-port S
An AW resonator, a piezoelectric substrate 32 and a comb-shaped electrode (IDT (Inter Digital Tr)
and a reflector 34 and the like.
【００２９】圧電基板３２は、例えば水晶で矩形板状に
形成されている。ＩＤＴ３３及び反射器３４は、圧電基
板３２の表面に導体金属を蒸着あるいはスパッタリング
等により薄膜状に形成した上で、フォトリソグラフィ等
によりすだれ状となるように形成されている。The piezoelectric substrate 32 is formed of, for example, quartz in a rectangular plate shape. The IDT 33 and the reflector 34 are formed in such a manner that a conductive metal is formed on the surface of the piezoelectric substrate 32 into a thin film by vapor deposition or sputtering or the like, and then interdigitated by photolithography or the like.
【００３０】本発明の特徴的な部分は、ＩＤＴ３３及び
反射器３４の形状にあり、以下に詳細に説明する。ＩＤ
Ｔ３３は、複数の電極指３３ａが所定のピッチで並設さ
れて長手方向の各端部が交互に短絡されるように形成さ
れている。即ち、２つの櫛形状の電極の各櫛歯部分が、
所定距離隔てて互い違いに入り込むように形成されてい
る。さらに、ＩＤＴ３３は、ＳＡＷの伝播方向の電極指
３３ａの幅に変化を付けて形成されている。即ち、電極
指３３ａにおける変化部分は、長さＬ3 の交差指の部分
のうち長さｌ3 の部分であって、ＳＡＷの伝播方向に延
びるＩＤＴ３３の中心線ＬC に対して対称の部分であ
り、この変化部分の幅ｗ3 が、他の部分の幅Ｗ3 より狭
くなるように形成されている。このＩＤＴ３３は、電気
的に接続されている外部端子３５を介して電気信号とＳ
ＡＷとの間の変換を行う機能を有する。A feature of the present invention lies in the shape of the IDT 33 and the reflector 34, which will be described in detail below. ID
T33 is formed such that a plurality of electrode fingers 33a are arranged side by side at a predetermined pitch, and each end in the longitudinal direction is alternately short-circuited. That is, each comb tooth portion of the two comb-shaped electrodes is
It is formed so as to alternately enter at a predetermined distance. Further, the IDT 33 is formed by changing the width of the electrode finger 33a in the SAW propagation direction. That is, the change portion in the electrode finger 33a is a part of the length l 3 of the portions of the interdigital length L 3, symmetrical parts with respect to the center line L C of IDT33 extending direction of propagation of the SAW There, the width w 3 of the change portion, is formed to be narrower than the width W 3 of the other part. This IDT 33 is connected to an electric signal via an external terminal 35 which is electrically connected.
It has a function of performing conversion to and from AW.
【００３１】反射器３４は、複数の電極指３４ａが所定
のピッチで並設されて長手方向の各両端部が短絡される
ように形成されている。そして、同一構成の２つの反射
器３４が、電極指３４ａがＩＤＴ３３の電極指３３ａと
平行になるように、かつＩＤＴ３３をＳＡＷの伝播方
向、即ちＩＤＴ３３の電極指３３ａの長手方向に直交す
る方向に所定距離隔てて挟み込むように形成されてい
る。さらに、反射器３４は、ＳＡＷの伝播方向の電極指
３４ａの幅に変化を付けて形成されている。即ち、電極
指３４ａにおける変化部分は、ＩＤＴ３３の変化部分を
ＳＡＷの伝播方向に延長させた部分であり、この変化部
分の幅ｗ33が、他の部分の幅Ｗ33より狭くなるように形
成されている。この反射器３４は、ＩＤＴ３３から伝搬
してくるＳＡＷを反射して、ＳＡＷのエネルギを内部に
閉じこめる機能を有する。The reflector 34 is formed such that a plurality of electrode fingers 34a are juxtaposed at a predetermined pitch and both ends in the longitudinal direction are short-circuited. The two reflectors 34 having the same configuration are arranged so that the electrode finger 34a is parallel to the electrode finger 33a of the IDT 33, and the IDT 33 is moved in the SAW propagation direction, that is, in the direction orthogonal to the longitudinal direction of the electrode finger 33a of the IDT 33. It is formed so as to be sandwiched at a predetermined distance. Further, the reflector 34 is formed by changing the width of the electrode finger 34a in the SAW propagation direction. That is, the change portion in the electrode finger 34a is a portion obtained by extending the change portion of the IDT33 the SAW propagation direction, the width w 33 of the change portion is formed to be narrower than the width W 33 of the other portion ing. The reflector 34 has a function of reflecting the SAW propagating from the IDT 33 and confining the SAW energy therein.
【００３２】このような構成において、電気信号が、外
部端子３５を介してＩＤＴ３３に入力されると、圧電効
果によりＳＡＷに変換される。このＳＡＷは、ＩＤＴ３
３の電極指３３ａの長手方向に対して直交方向に伝搬さ
れ、ＩＤＴ３３の両側から反射器３４に放射され、反射
器３４により多段反射されてＩＤＴ３３に戻される。こ
のとき、ＩＤＴ３３の電極指３３ａの電極周期ｄ3 に等
しい波長を持つＳＡＷが、最も強く励振される。In such a configuration, when an electric signal is input to the IDT 33 via the external terminal 35, it is converted into a SAW by a piezoelectric effect. This SAW is IDT3
The third electrode finger 33a propagates in a direction orthogonal to the longitudinal direction, is radiated to the reflector 34 from both sides of the IDT 33, is reflected by the reflector 34 in multiple stages, and returns to the IDT 33. At this time, SAW having wavelength equal to the electrode period d 3 of the electrode fingers 33a of the IDT33 is most strongly excited.
【００３３】さらに、ＩＤＴ３３の電極指３３ａ及び反
射器３４の電極指３４ａが、ＳＡＷの伝播直交方向に変
化して形成されているので、ＳＡＷの伝播速度も、ＳＡ
Ｗの伝播直交方向に変化する。このため、エネルギ閉じ
込め効果によりＳＡＷの変位が、電極指３３ａ、３４ａ
の細い部分に集中する。例えば、図３に示すように、従
来のＩＤＴ３の電極指３ａは、幅ｗ0 が長手方向にわた
って均一に形成されているため、Ａ−Ａ線断面における
交差指部分のＳＡＷの変位分布は、比較的ブロードにな
る。ところが、図４に示すように、本発明のＩＤＴ３３
の電極指３３ａは、長手方向中央の幅ｗ3 が長手方向両
側の幅Ｗ3 より狭くなるように形成されているため、Ｂ
−Ｂ線断面における交差指部分のうちの中央部分のＳＡ
Ｗの変位分布は、図３に比べてシャープになる。従っ
て、ＳＡＷの変位分布は、交差指幅を狭く設計したとき
と同様の変位分布となるので、図２に示すように、横モ
ードスプリアスが発生する周波数Ｆs は、交差指幅を狭
く設計したときと同様に、主振の動作周波数Ｆv から遠
ざかる。即ち、横モードスプリアスの周波数Ｆs と主振
の動作周波数Ｆv の差ΔＦが、図８に示す横モードスプ
リアスの周波数ｆs と主振の動作周波数ｆv の差Δｆよ
り大きくなり、周波数シフトのない、安定した発振を実
現することができる。また、電極指３３ａ、３４ａの太
い部分もＳＡＷを励振させるように作用するため、交差
指幅を広く設計したときと同様に特性を向上させること
ができる。このようなＳＡＷは、動作周波数Ｆv のみの
電気信号に変換されてＩＤＴ３３から外部端子３５を介
して出力される。Further, since the electrode fingers 33a of the IDT 33 and the electrode fingers 34a of the reflector 34 are formed so as to change in the direction orthogonal to the SAW propagation, the SAW propagation speed is also reduced.
It changes in the direction orthogonal to the propagation of W. For this reason, the displacement of the SAW due to the energy trapping effect causes the electrode fingers 33a, 34a
Focus on the narrow part of the. For example, as shown in FIG. 3, the electrode finger 3a of the conventional IDT 3 has a uniform width w 0 in the longitudinal direction. It becomes a target broad. However, as shown in FIG.
The electrode fingers 33a, since the longitudinal center width w 3 of is formed to be narrower than the width W 3 of the longitudinal sides, B
-SA at the central part of the cross fingers in the cross section taken along line B
The displacement distribution of W becomes sharper than that in FIG. Accordingly, the displacement distribution of the SAW, since the same displacement distribution and when narrowing designed cross finger width, as shown in FIG. 2, the frequency F s of the transverse mode spurious response is generated, narrowed designed interdigitated width Like the time, away from the operating frequency F v of the main vibration. That is, the difference ΔF of the frequency F s and Shufu operating frequency F v of the transverse mode spurious response, becomes larger than the difference Δf of the operating frequency f v of the frequency f s and Shufu transverse mode spurious shown in FIG. 8, the frequency shift And stable oscillation can be realized. Further, since the thick portions of the electrode fingers 33a and 34a also act to excite the SAW, the characteristics can be improved as in the case where the width of the cross fingers is designed wide. Such SAW is output from the operating frequency F v only be converted into an electric signal of IDT33 through the external terminal 35.
【００３４】図５は、本発明のＳＡＷデバイスの別の実
施形態を示す平面図である。FIG. 5 is a plan view showing another embodiment of the SAW device of the present invention.
【００３５】このＳＡＷデバイス４１は、トランスバー
サル型ＳＡＷフィルタであり、圧電基板４２とすだれ状
電極であるＩＤＴ４３等で大略構成されている。圧電基
板４２は、例えば水晶で矩形板状に形成されている。Ｉ
ＤＴ４３は、圧電基板４２の表面に導体金属を蒸着ある
いはスパッタリング等により薄膜状に形成した上で、フ
ォトリソグラフィ等によりすだれ状となるように形成さ
れている。The SAW device 41 is a transversal type SAW filter, and generally includes a piezoelectric substrate 42 and IDTs 43 which are interdigital electrodes. The piezoelectric substrate 42 is formed in a rectangular plate shape with, for example, quartz. I
The DT 43 is formed by forming a conductive metal on the surface of the piezoelectric substrate 42 into a thin film by vapor deposition or sputtering or the like, and then forming an IDT by photolithography or the like.
【００３６】本発明の特徴的な部分は、ＩＤＴ４３の形
状にあり、以下に詳細に説明する。ＩＤＴ４３は、複数
の電極指４３ａが所定のピッチで並設されて長手方向の
各端部が交互に短絡されるように形成されている。即
ち、２つの櫛形状の電極の各櫛歯部分が、所定距離隔て
て互い違いに入り込むように形成されている。さらに、
ＩＤＴ４３は、ＳＡＷの伝播直交方向の電極指４３ａの
変化部分の長さに重み付けして形成されていると共に、
ＳＡＷの伝播方向の電極指４３ａの幅に変化を付けて形
成されている。即ち、各電極指４３ａにおける変化部分
は、ＳＡＷの伝播方向に延びるＩＤＴ４３の中心線ＬC
を対称軸に全体として２分の１周期の正反転の余弦カー
ブ（図示一点鎖線）の内側部分であり、この変化部分の
幅ｗ4 が、他の部分の幅Ｗ4 より細くなるように形成さ
れている。A characteristic part of the present invention lies in the shape of the IDT 43, which will be described in detail below. The IDT 43 is formed such that a plurality of electrode fingers 43a are arranged side by side at a predetermined pitch and each end in the longitudinal direction is alternately short-circuited. That is, the respective comb teeth of the two comb-shaped electrodes are formed so as to alternately enter at a predetermined distance. further,
The IDT 43 is formed by weighting the length of the changing part of the electrode finger 43a in the direction orthogonal to the SAW propagation,
The width of the electrode finger 43a in the SAW propagation direction is changed. That is, the changed portion of each electrode finger 43a is the center line L C of the IDT 43 extending in the SAW propagation direction.
Is the inner portion of the cosine curve (dot-dash line in the figure) of the half inversion with respect to the symmetry axis as a whole, and the width w 4 of this changing portion is formed to be narrower than the width W 4 of the other portions. Have been.
【００３７】このように、電極指４３ａに対して重み付
けを実施することにより、図２に示す周波数Ｆs 付近の
横モードスプリアスの発生を低減することができる。ま
た、電極指４３ａの太い部分もＳＡＷを励振させるよう
に作用し、ＩＤＴ４３の全体を有効に利用することがで
きるので、従来のＩＤＴ１３の電極面積より小さくして
も十分なＳＡＷを励振させることができ、フィルタを小
型化することができる。[0037] Thus, by performing the weighted electrode finger 43a, it is possible to reduce the occurrence of transverse mode spurious response around a frequency F s shown in FIG. Also, the thick part of the electrode finger 43a acts to excite the SAW, and the entire IDT 43 can be effectively used. Therefore, even if the electrode area of the conventional IDT 13 is smaller, sufficient SAW can be excited. The size of the filter can be reduced.
【００３８】図６は、本発明のＳＡＷデバイスのさらに
別の実施形態を示す平面図である。FIG. 6 is a plan view showing still another embodiment of the SAW device of the present invention.
【００３９】このＳＡＷデバイス５１は、横結合型ＳＡ
Ｗフィルタであり、圧電基板５２とすだれ状電極である
ＩＤＴ５３及び反射器５４等で大略構成されている。圧
電基板５２は、例えば水晶で矩形板状に形成されてい
る。ＩＤＴ５３及び反射器５４は、圧電基板５２の表面
に導体金属を蒸着あるいはスパッタリング等により薄膜
状に形成した上で、フォトリソグラフィ等によりすだれ
状となるように形成されている。The SAW device 51 has a laterally coupled SA
This is a W filter, and is generally constituted by a piezoelectric substrate 52, IDTs 53 serving as interdigital electrodes, a reflector 54, and the like. The piezoelectric substrate 52 is formed in a rectangular plate shape, for example, from quartz. The IDT 53 and the reflector 54 are formed by depositing a conductive metal on the surface of the piezoelectric substrate 52 in a thin film shape by vapor deposition or sputtering, and then forming the IDT 53 in an interdigital shape by photolithography or the like.
【００４０】本発明の特徴的な部分は、ＩＤＴ５３及び
反射器５４の形状にあり、図１に示すＩＤＴ３３及び反
射器３４を電極指３３ａ、３４ａの長手方向に２組並べ
て結合配置した形状に形成されている。このように、Ｉ
ＤＴ５３の電極指５３ａ及び反射器５４の電極指５４ａ
の結合部の長手方向中央の幅ｗ5 、ｗ55が長手方向両側
の幅Ｗ5 、Ｗ55より狭くなるように形成されているた
め、交差指幅を狭く設計したときと同様の効果、即ちフ
ィルタの通過帯域幅を飛躍的に広帯域化させることがで
きる。また、電極指５３ａ、５４ａの太い部分もＳＡＷ
を励振させるように作用するため、特性インピーダンス
は増加せず、交差指幅を広く設計したときと同様に遅延
特性を向上させることができる。The characteristic part of the present invention lies in the shape of the IDT 53 and the reflector 54. The IDT 33 and the reflector 34 shown in FIG. 1 are formed in a shape in which two sets of the electrode fingers 33a and 34a are arranged and connected in the longitudinal direction. Have been. Thus, I
The electrode finger 53a of the DT 53 and the electrode finger 54a of the reflector 54
For longitudinal center of the width w 5, w 55 of the coupling portion is formed to be narrower than the longitudinal sides of the width W 5, W 55, the same effect as when the narrow design cross finger width, i.e. The pass band width of the filter can be dramatically increased. Also, the thick portions of the electrode fingers 53a and 54a are SAW
Therefore, the characteristic impedance does not increase, and the delay characteristic can be improved as in the case where the width of the interdigital finger is designed to be wide.
【００４１】尚、上述した図１及び図６に示すＳＡＷデ
バイス３１、５１では、反射器３４、５４の電極指３４
ａ、５４ａの幅も変化させるように構成したが、ＩＤＴ
３３、５３の電極指３３ａ、５３ａの幅のみ変化させる
ように構成してもよい。In the SAW devices 31 and 51 shown in FIGS. 1 and 6 described above, the electrode fingers 34 of the reflectors 34 and 54 are used.
a, 54a are also changed.
The width of the electrode fingers 33a, 53a of the electrodes 33, 53 may be changed.
【００４２】[0042]
【発明の効果】請求項１、２、３または４記載の発明に
よれば、弾性表面波の変位を電極指の変化部分に集中さ
せることができるので、各電極指の交差部分の長さを短
くすることなく、横モードスプリアスを主振から遠ざけ
ることができる。また、特性インピーダンスを増加させ
ることなく、通過帯域幅を広げることができる。According to the first, second, third or fourth aspect of the present invention, the displacement of the surface acoustic wave can be concentrated on the changing part of the electrode finger, so that the length of the intersection of each electrode finger can be reduced. The transverse mode spurious can be kept away from the main swing without shortening. Further, the pass bandwidth can be widened without increasing the characteristic impedance.
【００４３】請求項５または６記載の発明によれば、請
求項１、２、３または４記載の発明の効果に加え、すだ
れ状電極の面積を小さくすることができるので、弾性表
面波装置を小型化することができる。According to the fifth or sixth aspect of the invention, in addition to the effects of the first, second, third or fourth aspect of the present invention, the area of the interdigital transducer can be reduced. The size can be reduced.
【図１】 本発明のＳＡＷデバイスの実施形態を示す平
面図。FIG. 1 is a plan view showing an embodiment of a SAW device of the present invention.
【図２】 図１のＳＡＷデバイスにおける周波数特性を
示す図。FIG. 2 is a view showing frequency characteristics in the SAW device of FIG. 1;
【図３】 従来のＳＡＷデバイスにおけるＳＡＷの変位
分布を示す図。FIG. 3 is a diagram showing a SAW displacement distribution in a conventional SAW device.
【図４】 本発明のＳＡＷデバイスにおけるＳＡＷの変
位分布を示す図。FIG. 4 is a diagram showing a SAW displacement distribution in the SAW device of the present invention.
【図５】 本発明のＳＡＷデバイスの別の実施形態を示
す平面図。FIG. 5 is a plan view showing another embodiment of the SAW device of the present invention.
【図６】 本発明のＳＡＷデバイスのさらに別の実施形
態を示す平面図。FIG. 6 is a plan view showing still another embodiment of the SAW device of the present invention.
【図７】 従来のＳＡＷデバイスの一例を示す平面図。FIG. 7 is a plan view showing an example of a conventional SAW device.
【図８】 図７のＳＡＷデバイスにおける周波数特性を
示す図。FIG. 8 is a view showing frequency characteristics of the SAW device shown in FIG. 7;
【図９】 従来のＳＡＷデバイスの別の一例を示す平面
図。FIG. 9 is a plan view showing another example of a conventional SAW device.
【図１０】 従来のＳＡＷデバイスのさらに別の一例を
示す平面図。FIG. 10 is a plan view showing still another example of the conventional SAW device.
３１、４１、５１ ＳＡＷデバイス ３２、４２、５２ 圧電基板 ３３、４３、５３ ＩＤＴ（すだれ状電極） ３４、５４ 反射器（すだれ状電極） ３３ａ、３４ａ、４３ａ、５３ａ、５４ａ 電極指 ３５ 外部端子 31, 41, 51 SAW device 32, 42, 52 Piezoelectric substrate 33, 43, 53 IDT (interdigital electrode) 34, 54 Reflector (interdigital electrode) 33a, 34a, 43a, 53a, 54a Electrode finger 35 External terminal
Claims (6)
うすだれ状電極が形成されている圧電基板を備えた弾性
表面波装置において、 前記すだれ状電極が、前記弾性表面波の伝播方向の電極
指の幅に変化を付けて形成されていることを特徴とする
弾性表面波装置。1. A surface acoustic wave device comprising a piezoelectric substrate on which interdigital electrodes for converting between an electric signal and a surface acoustic wave are formed, wherein the interdigital electrode has a propagation direction of the surface acoustic wave. Wherein the width of the electrode finger is varied.
器で構成されており、少なくとも前記櫛形電極が、前記
弾性表面波の伝播方向の前記電極指の幅に変化を付けて
形成されている請求項１に記載の弾性表面波装置。2. The interdigital transducer comprises a comb electrode and a reflector, and at least the comb electrode is formed by changing the width of the electrode finger in the direction of propagation of the surface acoustic wave. The surface acoustic wave device according to claim 1.
部分が、前記弾性表面波の伝播方向に延びる前記すだれ
状電極の中心線に対して対称に形成されている請求項１
または２に記載の弾性表面波装置。3. The interdigital electrode of the interdigital transducer has a changing portion formed symmetrically with respect to a center line of the interdigital transducer extending in a propagation direction of the surface acoustic wave.
Or the surface acoustic wave device according to 2.
部分の幅が、他の部分の幅より狭くなるように形成され
ている請求項１、２または３に記載の弾性表面波装置。4. The surface acoustic wave device according to claim 1, wherein the width of the interdigitated portion of the interdigital electrode is smaller than the width of the other portion.
部分が、重み付けされて形成されている請求項１、２、
３または４に記載の弾性表面波装置。5. The method according to claim 1, wherein the changing portions of the interdigital electrodes in the electrode fingers are weighted.
5. The surface acoustic wave device according to 3 or 4.
直交方向の前記電極指の変化部分の長さである請求項５
に記載の弾性表面波装置。6. The weighting is a length of a change portion of the electrode finger in a direction orthogonal to the propagation of the surface acoustic wave.
A surface acoustic wave device according to claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35463198A JP3651291B2 (en) | 1998-12-14 | 1998-12-14 | Surface acoustic wave device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35463198A JP3651291B2 (en) | 1998-12-14 | 1998-12-14 | Surface acoustic wave device |
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| Publication Number | Publication Date |
|---|---|
| JP2000183681A true JP2000183681A (en) | 2000-06-30 |
| JP3651291B2 JP3651291B2 (en) | 2005-05-25 |
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ID=18438865
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|---|---|---|---|
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| Country | Link |
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| JP (1) | JP3651291B2 (en) |
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| JP2012186808A (en) * | 2011-03-07 | 2012-09-27 | Triquint Semiconductor Inc | Acoustic wave guide device and method for minimizing trimming effects and piston mode instabilities |
| US8390400B2 (en) | 2007-03-27 | 2013-03-05 | Murata Manufacturing Co., Ltd. | Acoustic wave element having an electrode finger with a protrusion |
| JP2013518455A (en) * | 2010-01-25 | 2013-05-20 | エプコス アーゲー | Electroacoustic transducer with improved performance by reducing lateral radiation loss and suppressing lateral mode |
| WO2015182521A1 (en) * | 2014-05-26 | 2015-12-03 | 株式会社村田製作所 | Elastic wave device and ladder-type filter |
| US20160072475A1 (en) * | 2013-05-29 | 2016-03-10 | Murata Manufacturing Co., Ltd. | Elastic wave device |
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| CN111492575A (en) * | 2017-12-19 | 2020-08-04 | 株式会社村田制作所 | Elastic wave device |
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1998
- 1998-12-14 JP JP35463198A patent/JP3651291B2/en not_active Expired - Fee Related
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| US8390400B2 (en) | 2007-03-27 | 2013-03-05 | Murata Manufacturing Co., Ltd. | Acoustic wave element having an electrode finger with a protrusion |
| US8085116B2 (en) * | 2008-03-24 | 2011-12-27 | Taiyo Yuden Co., Ltd. | Elastic wave device with a dielectric layer on the comb-shaped electrodes |
| US9673779B2 (en) | 2010-01-25 | 2017-06-06 | Qualcomm Incorporated | Electroacoustic transducer having reduced losses due to transverse emission and improved performance due to suppression of transverse modes |
| JP2013518455A (en) * | 2010-01-25 | 2013-05-20 | エプコス アーゲー | Electroacoustic transducer with improved performance by reducing lateral radiation loss and suppressing lateral mode |
| JP2014131351A (en) * | 2010-01-25 | 2014-07-10 | Epcos Ag | Electroacoustic transducer having performance enhanced by reducing lateral direction radiation loss and suppressing lateral direction mode |
| US9257960B2 (en) | 2010-01-25 | 2016-02-09 | Epcos Ag | Electroacoustic transducer having reduced losses due to transverse emission and improved performance due to suppression of transverse modes |
| JP2012186808A (en) * | 2011-03-07 | 2012-09-27 | Triquint Semiconductor Inc | Acoustic wave guide device and method for minimizing trimming effects and piston mode instabilities |
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| CN109787578A (en) * | 2018-11-30 | 2019-05-21 | 无锡市好达电子有限公司 | A kind of SAW filter of interdigital structure overcompensation |
| WO2021013568A1 (en) * | 2019-07-22 | 2021-01-28 | RF360 Europe GmbH | Electro acoustic resonator with reduced spurious modes, rf filter and multiplexer |
| CN110572136B (en) * | 2019-09-09 | 2022-11-01 | 杭州左蓝微电子技术有限公司 | Interdigital transducer |
| CN110572136A (en) * | 2019-09-09 | 2019-12-13 | 杭州左蓝微电子技术有限公司 | interdigital transducer |
| WO2023219170A1 (en) * | 2022-05-13 | 2023-11-16 | 株式会社村田製作所 | Elastic wave device and filter device |
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